1. Field of the Invention
The present invention relates to a spring height adjusting device for truck (not only bogie truck but also ordinary single truck) of railroad vehicles and, more particularly, to a device for adjusting the height of the floor of the vehicle chassis from the rail surface, the chassis being mounted on and supported by the truck through a spring device.
2. Description of the Prior Art
Generally, the tread surfaces of wheels of railroad vehicles are worn during long use thereby reducing the diameters of the wheels. In addition, mechanical work such as grinding is conducted periodically on the treads of wheels to maintain precisely circular form of the wheels. As a consequence, the height or level of the chassis floor from the ground level is decreased by an amount corresponding to the reduction in diameter of the wheels. It is, therefore, necessary to correct or readjust the chassis floor level from the ground level in the factory as required.
In a railroad vehicle, a spring device (coiled spring or pneumatic spring) is disposed between the chassis and transverse beam or longitudinal member equivalent in effect to the transverse beam (such beam or member will be referred to as "base member" hereinunder regardless of the authorized technical term which varies depending on the construction and type of the truck). The correction or readjustment of the height of the chassis floor is usually made by inserting an adjusting plate or plates of predetermined thickness between the lower surface of a spring retainer which may be integral with the spring and the upper surface of the truck, or alternatively, between the upper surface of the spring retainer and the lower surface of the chassis.
A typical example of such adjustment will be explained in connection with FIG. 1 (prior art). A two-axle bogie truck generally designated by a numeral 1 has a pair of base members or side frames 2 arranged at both sides along the length of the railroad truck. A wheel set 6 is rotatably attached to each end of each base member 2 through an axle spring 3, axle box 4 and an axle 5. The weight of the chassis 8 is born by a coiled spring 7 which is prevented, by a spring retainer 7a, from moving in the horizontal direction. In order to adjust the spring height, an adjusting plate 9 of a suitable thickness is placed in contact with the lower surface of each spring retainer 7a. Namely, at each side of the chassis, the adjusting plate 9 is disposed and fixed to the base member 2 at longitudinally mid point of the latter. More specifically, a center pin 7b projecting from the lower surface of the spring retainer 7a is fitted in a locating bore formed in a predetermined portion of the upper surface of the base member 2. A central hole formed in the adjusting plate 9 receives the center pin 7b of the spring retainer.
For correcting or readjusting the spring height, i.e., the height or level of the floor of the chassis 8 from the level of the upper face of the rail 10, the spring retainer 7a is raised together with the chassis 8 and the spring 7 by a jack or the like means (not shown) until the center pin 7b of the spring retainer 7a completely clears the hole in the base member 2. Then, an adjusting plate 9 of a required thickness is inserted laterally into the gap formed between the lower end of the spring retainer 7a and the upper face of the base member 2. After obtaining a substantial axial alignment of the center pin 7b, hole in the base member 2 and the central hole 9a of the adjusting plate 9, the spring retainer 7a is lowered together with the chassis 8 and the spring 7 so that the center pin 7b fits in the hole in the base member 2 through the central hole 9a of the adjusting plate. In consequence, the height or level of the floor of the chassis 8 is increased by an amount corresponding to the increase of the thickness of the adjusting plate 9 interposed between the lower face of the spring retainer 7a and the base member 2, thus completing the correction or readjustment of the level from the rail surface.
Thus, the correction or readjustment is made in accordance with the change or decrease of the radius of the tread surface of the wheel 6 by stacking a plurality of adjusting plates of suitable thicknesses or by means of a single adjusting plate having a thickness equal to the total thickness of the stacked adjusting plates, in the manner explained hereinbefore. This conventional method of the height correction or readjustment requires a multiplicity of adjusting plates of a large variety of thicknesses to be stored in the factory. The administration of the adjusting plate is very troublesome and requires much labor. The work itself for the correction or readjustment of height is troublesome. It is often experienced that the chassis is inconveniently declined due to inadequate height readjustment at both sides, i.e., by the use of adjusting plates of different thicknesses between the base members 2 and the spring retainers 7 at both sides of the chassis.